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Successful completion of One Year of Service by SCATSAT-1 Scatterometer

SCATSAT-1, the state-of-the-art satellite with a dedicated Scatterometer payload was launched on September 26, 2016. It is a continuity mission for Oceansat-2 Scatterometer (OSCAT) to provide wind vector data products for weather forecasting, cyclone detection and tracking services to the users. SCATSAT-1 inherits the design of OSCAT, hence operates in Ku-band having 13.53GHz central frequency and having a pencil beam design with two beams with incidence angles of 490 and 570 on ground with HH and VV polarization respectively. With a swath width of 1800 km, this instrument covers 90% of the earth’s surface in a single day. With the experience gained through OSCAT, a few improvements have been made to the sensor characteristics for better sensitivity in backscatter especially in Polar Regions.

The radar backscatter measurement of SCATSAT-1 has commenced with the switch-on of main TWTA (Traveling Wave Tube Amplifier) on October 03, 2016. The instrument had undergone calibration and validation (Cal-Val) phase during which sensor stability monitoring, fine-tuning of algorithms have taken place. As the sensor is providing very high quality observations without any glitch, which provided good confidence on the instrument performance and led to the early public release of wind products (Beta version) through MOSDAC and NRSC as a Beta version on October 22, 2016. Subsequently after successful completion of the Cal-Val phase, the mission entered into operational phase from April 21, 2017.

The main operational products from this mission are global ocean surface wind products at 25 km and 50 km swath grids. Apart from this, various value added products such as (1) High Resolution Winds at 6.25 km swath grid (2) Daily Analysed Winds (3) High Resolution Sigma0 products over land and polar regions are routinely generated and disseminated to the user community through MOSDAC.

SCATSAT-1 provided invaluable wind observations during various cyclones such as Matthew, Hima, Nina, Nada, Vardha, Maarutha, Moora, Harvey and Irma etc., Apart from this, the SCATSAT-1 wind products are able to cater to various application like - improved weather forecast through data assimilation in NWP models, improved Cyclone track and intensity prediction, improved ocean state forecast through SCATSAT-1 derived wind forcing. SCATSAT-1 derived ocean surface winds are being operationally assimilated by National Centre of Medium Range Weather Forecasting (NCMRWF), MoES and Space Applications Centre, ISRO in Numerical Atmospheric Weather Prediction Model to improve the predictions. Moreover, using the SCATSAT-1 measured backscatter data, land applications like soil moisture estimation and hydrological applications such as river water level change detection studies etc., and polar studies of studying the spatio-temporal variability of Ice coverage are well demonstrated.

Analysis of SCATSAT-1 super resolution data derived sea ice had revealed that the seasonal minima of the Antarctic sea ice (occurred in the first week of March 2017) and the seasonal maxima (occurred on September 15, 2017) were delayed with respect to 2016. An animation prepared from sea ice images from January to September 15, 2017 is shown below. The sea ice derived from SCATSAT-1 is shown against the median value of sea ice extent from 1978 to 2010 (usually this is taken as climatological sea ice behaviour) is also shown. It is clear from the chart that this year the sea ice remained below normal (1981-2010 median value) for all the months.

The SCATSAT-1 data is extensively used on daily basis by both National as well as International users. It provided valuable input data to the global community in the area of weather forecasting and cyclone detection & tracking.

Snapshot of high-resolution winds captured by SCATSAT during cyclone Vardha in Bay of Bengal on December 10, 2016

Life cycle of winds captured by SCATSAT during cyclone Irma in North Atlantic Ocean during August 24 to September 01, 2017

Sea ice seasonal variations depicted through SCATSAT-1 from December 2016 to September 15, 2017 (Left, animation). The right part shows SCATSAT-1 derived sea ice (Red Line) in comparison to the long term median sea ice from 1981-2010 (Blue line)